1. Field of the Invention
The present invention relates to a control system for controlling changeover or switching of speed-change patterns for an automatic transmission mounted on a motor vehicle in dependence on driving/operation information such as information of driving or running state of the motor vehicle and information of operation states of an internal combustion engine mounted on the motor vehicle as well as that of the transmission. More specifically, the present invention is concerned with a speed-change pattern switching control system for the automatic transmission of the motor vehicle which system can ensure comfortableness of driving the motor vehicle in an automatic speed change mode (or automatic transmission shift mode) validated after resetting of a manual speed change mode (or manual transmission shift mode) by storing proper reference data acquired on the basis of the driving/operation information during a period in which the motor vehicle is driven in the manual speed change mode with the transmission (also known as the speed change gear) being manipulated or shifted manually by the driver.
2. Description of Related Art
Heretofore, the automatic transmission for the motor vehicles which is automatically shifted in accordance with speed-change patterns set previously in conformance with the driving/operation information is well known in the art. At this juncture, it is also noted that many of the automatic transmissions of this type are so designed that a manual speed change mode can be selectively effectuated or validated with a view to making it possible to change the speed of the motor vehicle manually by the driver so as to reflect his or her will or preference in the running behavior of the motor vehicle or to manipulate the motor vehicle at liberty of the driver, to say in another way.
Furthermore, in order to ensure comfortableness of individual drivers in driving the motor vehicle which may differ from one to another driver, there have been proposed and developed various systems for controlling the changeover or switching of the speed-change patterns themselves in dependence on the driving/operation information mentioned previously.
For having better understanding of the invention, a background technique thereof will be described in some detail. FIG. 5 is a flow chart for illustrating operations of a hitherto known or conventional speed-change pattern switching control system for an automatic transmission of a motor vehicle described, for example, in Japanese Unexamined Patent Application Publication No. 167272/1995(JP-A-7-167272) or No. 167274/1995(JP-A-7-167274). The processing procedure illustrated in FIG. 5 is executed by a processor incorporated in an electronic control unit (hereinafter also referred to as the ECU for short) mounted on a motor vehicle. Further, FIG. 6 is a view for graphically illustrating exemplary speed-change patterns in a conventional automatic transmission.
Now, referring to FIGS. 5 and 6, description will be made of operations of the conventional speed-change pattern switching control system for the automatic transmission of the motor vehicle.
Referring to FIG. 5, the ECU fetches driving/operation information detected by various sensors mounted in association with the internal combustion engine of the motor vehicle such as engine torque Te, vehicle speed Vs, throttle opening degree .theta., etc.) in a step S1, to thereby decide the running or driving state of the motor vehicle on the basis of the operation state or performance of the engine mounted on the motor vehicle in a step S2. Further, the ECU decides the running or driving state of the motor vehicle on the basis of tire performance (step S3).
Subsequently, the ECU makes decision as to whether the current driving/operation information indicates the manual speed change mode or the automatic speed change mode in a step S4. When the driving/operation information indicates the automatic speed change mode (i.e., when the decision step S5 results in negation "NO"), information concerning the driving/operation state of the motor vehicle is acquired in a step S5, whereon changeover or switching of the speed-change patterns for the automatic transmission mode (automatic speed change mode) is carried out on the basis of speed-change pattern decision reference data derived from the acquired information in a step S6.
On the other hand, when it is decided in the step S4 that the current driving/operation information indicates the manual speed change mode (i.e., when the decision step S4 results in affirmation "YES"), the speed-change pattern decision reference data used in the automatic speed change mode is erased to thereby initialize the speed-change pattern switching information (step S7).
Through the processing procedure described above, the speed-change pattern can be switched on the basis of the speed-change pattern decision reference data derived from the information of the driving/operation state of the motor vehicle in the automatic speed change mode. By way of example, referring to FIG. 6, the speed-change pattern set initially (indicated by a solid line curve) can be shifted to a mild pattern or sporty pattern indicated by broken line curves, respectively, in conformance with the driving/operation state of the motor vehicle in the automatic speed change mode.
More specifically, when the operator or driver desires to enjoy a sporty drive, so to speak, the speed-change pattern is shifted to the sporty pattern such as illustrated in FIG. 6. In that case, the vehicle speed changes from a value Vsu to a value Vss for a same throttle opening degree .theta..degree..
By contrast, when the operator or driver desires to enjoy a so-called mild drive, the speed-change pattern is shifted to a mild pattern illustrated in FIG. 6. In that case, the vehicle speed changes from the value Vsu to a value Vsm for a same throttle opening degree .theta..degree..
In this manner, in the automatic speed change mode, the speed-change pattern is changed over on the basis of the speed-change pattern decision reference data set previously in dependence on the road condition and the running state of the motor vehicle. More specifically, through the speed-change pattern switching control described above, the speed-change pattern can be changed finely in dependence on the speed-change pattern decision reference data derived from the driving/operation information.
On the other hand, when the manual speed change mode is selected or validated, the speed-change pattern decision reference data to be referenced in switching or shifting the speed-change pattern is reset for the reason that in the manual speed change mode, the speed change is not carried out in accordance with the speed-change pattern.
It is further noted that even when the speed-change pattern decision reference data is held or stored intactly in the manual speed change mode, the speed-change pattern decision reference data as held cannot always match with the running state of the motor vehicle prevailing when the automatic speed change mode is restored from the manual speed change mode. Besides, it should also be mentioned that the information which is not required for the system control in general should desirably be reset positively to the initial state.
For the reasons mentioned above, when the driver selects the manual speed change mode, the speed-change pattern decision reference data employed in the automatic speed change mode is erased or reset with the speed-change pattern being set back to the initially set pattern.
Such being the circumstances, when the automatic speed change mode is restored with the manual speed change mode being reset, there arises necessity of determining the speed-change pattern decision reference data on the basis of the driving/operation information by executing the information processing procedure described previously from the beginning thereof. In that case, unnecessary speed change operation will have to be performed repetitively over an extended time period which is required for the speed-change pattern decision reference data to converge to the pertinent value.
As will now be appreciated from the foregoing, in the case of the conventional speed-change pattern switching control system for the automatic transmission of the motor vehicle, the speed-change pattern decision reference data for the speed pattern changeover or switching is erased when the manual speed change mode is selected by the driver, which necessitates acquisition of the driving/operation information newly for determining the speed-change pattern decision reference data upon restoration of the automatic speed change mode from the manual speed change mode, presenting thus a problem that a lot of time is taken for determining the pertinent speed-change pattern decision reference data by repeating unnecessary speed changing manipulation.